[5] It forms one of the westerly outposts of the chalk hills called the South Downs, and rises to a maximum height of about 210 metres above sea-level.

Gilbert White, in his Natural History of Selborne, says of Noar Hill: At each end of the village [Selborne], which runs from south-east to north-west, arises a small rivulet: that at the north-west end frequently fails: but the other is a fine perennial spring little influenced by drought or wet seasons, called Well-head.

This breaks out of some high grounds adjoining to Nore Hill, a noble chalk promontory, remarkable for sending forth two streams into two different seas.

These include hairy rock-cress (Arabis hirsuta), dropwort (Filipendula vulgaris), harsh downy-rose (Rosa tomentosa), pale flax (Linum bienne), common milkwort (Polygala vulgaris), marjoram (Origanum vulgare), wild thyme (two species: large thyme (Thymus pulegioides) and mother-of-thyme (Thymus polytrichus)), eyebright (Euphrasia nemorosa), and clustered bellflower (Campanula glomerata).

High Common, surrounded by botanically impoverished farmland, provides both a refuge for chalk downland species and a reservoir from which recolonization of nearby areas is possible.

Noar Hill is home to the only British species of the curious fairy shrimp (Chirocephalus diaphanus), which lives in puddles on the tracks and survives as an egg when the mud dries.

It supports breeding turtle doves (Streptopelia turtur); and green woodpeckers (Picus viridis), which are fond of feeding on ants, are frequent.